https://github.com/Discookie created
https://github.com/llvm/llvm-project/pull/131575
Relands #129502.
Previously when the framework encountered unsupported values (such as enum
classes), they were always treated as equal when comparing with `==`,
regardless of their actual values being different.
Now the two sides are only equal if there's a Value assigned to them.
Added handling for the special case of `nullptr == nullptr`, to preserve the
behavior of untyped `nullptr` having no value.
>From b5079e0be2392c71143d71543dadf735c0245518 Mon Sep 17 00:00:00 2001
From: Viktor <viktor.c...@ericsson.com>
Date: Mon, 17 Mar 2025 07:11:44 +0000
Subject: [PATCH] [clang][dataflow] Fix unsupported types always being equal
Previously when the framework encountered unsupported values, they were always
treated as equal when comparing with `==`, regardless of their actual values
being different.
Now the two sides are only equal if there's a Value assigned to them.
Added handling for the special case of `nullptr == nullptr`, and preserved
untyped `nullptr` having no value.
---
clang/lib/Analysis/FlowSensitive/Transfer.cpp | 9 ++++-
.../Analysis/FlowSensitive/TransferTest.cpp | 35 +++++++++++++++++++
2 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Analysis/FlowSensitive/Transfer.cpp
b/clang/lib/Analysis/FlowSensitive/Transfer.cpp
index 9c54eb16d2224..6403190723e69 100644
--- a/clang/lib/Analysis/FlowSensitive/Transfer.cpp
+++ b/clang/lib/Analysis/FlowSensitive/Transfer.cpp
@@ -60,7 +60,14 @@ static BoolValue &evaluateBooleanEquality(const Expr &LHS,
const Expr &RHS,
Value *LHSValue = Env.getValue(LHS);
Value *RHSValue = Env.getValue(RHS);
- if (LHSValue == RHSValue)
+ // When two unsupported values are compared, both are nullptr. Only supported
+ // values should evaluate to equal.
+ if (LHSValue == RHSValue && LHSValue)
+ return Env.getBoolLiteralValue(true);
+
+ // Special case: `NullPtrLiteralExpr == itself`. When both sides are untyped
+ // nullptr, they do not have an assigned Value, but they compare equal.
+ if (LHS.getType()->isNullPtrType() && RHS.getType()->isNullPtrType())
return Env.getBoolLiteralValue(true);
if (auto *LHSBool = dyn_cast_or_null<BoolValue>(LHSValue))
diff --git a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
index 0f731f4532535..f52b73dbbdc57 100644
--- a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
@@ -4974,6 +4974,41 @@ TEST(TransferTest, IntegerLiteralEquality) {
});
}
+TEST(TransferTest, UnsupportedValueEquality) {
+ std::string Code = R"(
+ // An explicitly unsupported type by the framework.
+ enum class EC {
+ A,
+ B
+ };
+
+ void target() {
+ EC ec = EC::A;
+
+ bool unsupported_eq_same = (EC::A == EC::A);
+ bool unsupported_eq_other = (EC::A == EC::B);
+ bool unsupported_eq_var = (ec == EC::B);
+
+ (void)0; // [[p]]
+ }
+ )";
+ runDataflow(
+ Code,
+ [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+ ASTContext &ASTCtx) {
+ const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+ // We do not model the values of unsupported types, so this
+ // seemingly-trivial case will not be true either.
+ EXPECT_TRUE(isa<AtomicBoolValue>(
+ getValueForDecl<BoolValue>(ASTCtx, Env, "unsupported_eq_same")));
+ EXPECT_TRUE(isa<AtomicBoolValue>(
+ getValueForDecl<BoolValue>(ASTCtx, Env, "unsupported_eq_other")));
+ EXPECT_TRUE(isa<AtomicBoolValue>(
+ getValueForDecl<BoolValue>(ASTCtx, Env, "unsupported_eq_var")));
+ });
+}
+
TEST(TransferTest, CorrelatedBranches) {
std::string Code = R"(
void target(bool B, bool C) {
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